test-documentation: Factor out the terminal goo for coloring messages.

tools/test-documentation

@@ -1,6 +1,10 @@
 #!/usr/bin/env bash
 set -e
 
+color_message () {
+    local color_code="$1" message="$2"
+    echo -e "\e[${color_code}m${message}\e[0m"
+}
 
 case $1 in
     -h|--help)
@@ -22,22 +26,16 @@ rm -rf _build
 # The crawler would take a very long time to finish and TravisCI would fail as a result.
 sphinx-build -j8 -b html -d _build/doctrees -D html_theme_options.collapse_navigation=True . _build/html
 
-echo -en "\033[0;94m"
-echo "Testing links in documentation..."
-echo -en "\033[0m"
+color_message 94 "Testing links in documentation..."
 
 cd ../tools/documentation_crawler
 set +e
 scrapy crawl_with_status documentation_crawler $loglevel
 result=$?
 if [ "$result" = 1 ]; then
-    echo -en "\033[0;91m"
-    echo "Failed!"
-    echo -en "\033[0m"
+    color_message 91 "Failed!"
     exit 1
 else
-    echo -en "\033[0;92m"
-    echo "Passed!"
-    echo -en "\033[0m"
+    color_message 92 "Passed!"
     exit 0
 fi